Spark discharge sound generator



May 19, 1959 A. G.'BQDINE, JR., ETAL 2,837,604

SPARK DISCHARGE souma GENERATOR Fifed June 27, 1955 FIG. 5 56 4 WA"? EQF I G. 2

INVENTOR.

ALBERT G. BODINE JR. JAMES D. STOAKES United States PatentO F SPARKDISCHARGE SOUND GENERATOR Albert G. Bodine, In, Van Nuys, and James D.Stoakes, North Hollywood, Calif.; said Stoakes assignor to said BodineApplication June 27, 1955, Serial No. 518,034

9 Claims. (Cl. 313-432) This invention relates generally to sparkdischarge sound generators, and a primary object of the invention is theprovision of a high power spark sound unit for such a generator.

Spark sources of sound are discussed in the standard acoustic textbooks. They have uses both as sources of sound, as such, and in variousindustrial processes where high amplitude sound waves are applied toeffect or aid certain desired physical or chemical process steps. Thepresent invention is characterized by a spark source which yields agreatly lengthened spark through a special air gap for a given impressedvoltage. Generally speaking, the breakdown voltage for an air gap isabout 20,000 volts per inch. We have discovered a novel air spark gapbounded by a water surface across which a very greatly lengthened sparkmay be obtained for a given impressed voltage, yielding greatlyaugmented sound power. The invention may be best described byreferring'at once to the drawings, in which:

Fig. 1 shows diagrammatically a spark source set-up in accordance withthe invention;

Fig. 2 shows a modification, equipped with a sound radiating reflector;

Fig. 3 is a section taken on line 33 of Fig. 2;

Fig. 4 is a diagrammatic illustration of a further embodiment; and

Fig. 5 is a diagrammatic illustration of still another embodiment.

In Fig. 1, numeral designates a shallow pan, typically.

A DC power supply of suitable voltage, typically.

12,000 volts, is designated at 14, and one terminal there of, forexample, the grounded negative terminal, is connected by lead to theexposed terminal portion 13 of electrode 12. v

The opposite electrode 16, here shown to comprise a pointed pin 17carried by a pivotally mounted switch arm 18, is disposed with its point170 approximately over the electrode 12. The switch arm 18 is springactuated to assume a normal or charging position such as shown in fulllines, and may be depressed from such position to cause the electrodetip to approach the water level over the submerged electrode 12, asindicated in the dotted lines. In the uppermost position of the arm, aterminal 17b on the upper end of the electrode pin 17 makes contact witha switch contact arm 20, which is shown as connected by lead 21 to thepositive terminal of the power supply unit. A large condenser 22, forexample, 100

mf., is connected across lead 15 and terminal 17b; and I it will be seenthat when the switch arm 18 is in its upper 2,887,604 Patented May 19,1950 water surface, a powerful spark discharge takes place from theelectrode tip 17a to the surface of the water, and thence along thesurface of the water, directly over the electrode 12, to the exposedterminal portion 13 of said electrode. With a 12,000 volt power supply,we have in this way obtained a spark of a length as great as 22". Thegap jumped by the spark is thus through air from the electrode tip 17ato a point x at the water surface, located directly over the electrode12, and thence through air but directly over and in close proximity tothe surface of the water to the terminal 13. The spark obtained iswhitish-blue in color, very intense, and is accompanied by a loud, sharpcrack. The condenser alternately charges and discharges as the switcharm 18 is elevated and depressed. Obviously, electronic switching can besubstituted for the simple mechanical switch here shown for purpose ofsimple illustration.

We have found that the water used, if too electrically conductive, asfor instance if salt be dissolved therein, will result in the sparkdiving to the submerged electrode 12. It may either do so at once, ormay travel a distance toward the terminal 13 before penetrating thewater and striking the electrode 12. We have found ordinary city tapwater to be entirely operative. If too conductive'in any given case, itmay be mixed with distilled water until suitable dielectric propertiesare attained. We have re-- versed the polarity of the electrodes 12 and16, and detected no difference in operation.

After extended study and laboratory experiment, we still find theunderlying principle of operation of this spark source to be more orless obscure. A process of progressive ionization at the water surfaceis evidently involved. The water body is a source of negative ions whichwill evidently be attracted to the water surface by the positive ionsfrom the air above. The electric field between the electrodes 16 and 12is of very high voltage gradient adjacent the electrode tip 17a,suggesting ionization in the air space above the water as a mechanism bywhich the spark may be initiated. The initial striking surface above thetip of electrode 12 may be accounted for either by such ionization ofthe air, by a reduced potential difference between the water level andthe electrode tip 17a owing to an accumulation of negative ions at thewater surface, or by the approach of the electrode 17a toward thesubmerged electrode 12, or some combination of such factors. In anyevent, the path through the water, which constitutes a slightlyconductive dielectric layer in series with the air gap between theelectrode tip 17a and the point x at the water level, is not penetratedby the spark in proper operation though the possibility of someconduction of current through the water is not excluded. Instead, thespark follows the path along the water surface from the point x to theterminal 13. The breakdown of this gap portion x to 13 along the watersurface above the electrode 12 may tentatively be explained by the factthat the point of gap from the point 17a to x. The electron flow doesnot short through to the electrode 12 because of the di-- electricstrength of the water. As the point of greatest electrical strainrecedes along the electrode 12 (following,

initial striking from the electrode tip 17a) the gap portion x to 13along the water surface progressively breaks down and is bridged by theelectron avalanche.

Referring now to Figs. 2 and 3, there is shown a modified form ofgenerator embodying the invention, characterized by employment of awetted wick in place of the pan of water of the first describedembodiment, and showing also the use of a parabolic sound wave reflectorin combination with the spark source unit. The elongated electrode orantenna, corresponding to the electrode 12 of the first describedembodiment, is here designated at 30, and is surrounded by a wick 31whose upper end dips into a water filled container 32, so that the wickbecomes saturated and surrounds the electrode with a layer of water. Theopposite electrode comprises a conductive ring or band 33 surroundingthe wetted wick 31 and the upper end portion of the antenna 30. Aparabolic sound wave reflector 35 surrounds the source unit, its upperend wall being suitably apertured for passage of the wick, as clearlyshown in Fig. 2. The wick 31 and electrode 30 may be supported by asuitable insulation mounting 36 suitably secured to the wall of thereflector.

One power lead 36 is connected to electrode 33, and the other power lead37 is connected to the lower extremity of the electrode 30, a resistor38 being shown in series with the power lead 36, and a condenser 39being connected across the leads 36 and 37.

In operation, a voltage impressed across the leads 36 and 37 charges thecondenser 39 through the resistor 38 until the voltage across thecondenser reaches the breakdown level. As in the first embodiment, thespark does not strike from the electrode 33 through the water held bythe wick directly to the electrode 30, but travels longitudinally alongthe exterior surface of the wetted wick between the electrode 33 and theexposed lower extremity of the electrode 30. Thus, as in the case ofFig. 1, there is a water layer between the extended electrode or antennaand the opposite electrode, and a spark is drawn from the latter alongthe exterior surface of this water layer or barrier parallel to theantenna to its exposed lower extremity. The spark extinguishes as soonas the condenser 39 is discharged, the resistance 38 being too great tomaintain the heavy current fiow. After the spark is extinguished thisshort circuit no longer exists, and the relatively small current throughresistor 38 can then charge the condenser again, until breakdown, andthus the cycle is automatically repeated. This form of the inventiondoes not require a switching mechanism because the cycle automaticallyrepeats at a frequency determined by the power source across leads 36and 37, the values of resistor 38 and condenser 39, and the breakdownvoltage of the spark. It is a relaxation oscillator. This relaxationoscillator is usable with many species of the invention.

Reference is next directed to Fig. 4, showing another embodiment ofspark source. Numeral 40 designates a container filled with water to thelevel 41. Numeral 42 designates an insulation (acrylic resin barextending down into the water. An elongated electrode rod or antenna 43is placed substantially parallel to the bar 42 and its lower terminalportion is attached to the lower end thereof as at 44. One power lead 45is attached to the electrode terminal at 44. The other power lead 46 istouched down to the water surface at 47, using any suitable switchingdevice. In this case, a spark travels over the surface of the water from47 to a point a where the acrylic bar 42 emerges from the water, andthen travels down the surface of the bar 42, parallel to the electrode43, to the terminal 44 at the bottom. This form of the inventionsuggests either that a water-air interface is not necessary, or elsethat a sufficient 'film of air clings to the surface of the bar 42.

A still further under-water spark source in accordance with theinvention is shown in Fig. 5. In this case, an

acrylic or other insulation bar 50 is mounted so as to extend downwardlyinto a container 51 holding a body of water whose surface is at 52.Preferably, for a reason which will appear presently, the bar 50 isinclined somewhat from vertical. Along the uppermost edge of the bar 50is placed an elongated electrode rod or strap 53. The upper end portion53a of the electrode strap 53 extends transversely through an opening inthe upper end portion of the bar 50 so as to protrude somewhat frommember 50. A power lead 54 is connected to the lower end of strap 53.The opposite electrode comprisses a conductive terminal element 55 setinto the lower portion of bar 50 on the opposite side from the strap 53,and to this terminal member or electrode 55 is connected the oppositepower lead 56. The spark gap then consists of a path along the surfaceof the insulation member 50 between the electrode element 55 and theprotruding extremity 53a of the elongated electrode member 53. An airsupply hose 57 supplies air to a point near the lower end of theinclined bar 50, so as to rise through the water along the surface ofthe bar 50 between the two spark terminals. Application of a suflicientvoltage across the leads 54 and 56 results in a spark traveling alongthe gap between elements 53a and 55, the gap being the interface regionbetween the water and the bar 50.

It will be understood that for sound wave generation, the spark sourcesabove described may be furnished with suitable sound wave reflectors, asin Figs. 2 and 3; or may be used without such reflectors. The embodimentof Fig. 5 is particularly suited to under-water generation to soundwaves for promotion of various industrial processes.

The foregoing illustrative examples demonstrate several of numerous waysin which the invention may be practiced, and it will be understood thatthe examples given are merely illustrative and not exhaustive of theforms which the invention may take in practice. The characteristicfeature is a Water surface bounding a spark gap, with an elongatedelectrode substantially parallel to but separated by a dielectricsubstance from the water surface. In some forms, the water surface is awater-air interface between bodies of water and air. In others, thewater surface is bounded by a solid dielectric medium. All suchmodifications, and others, are within the broad scope of the inventionas defined by the appended claims.

We claim:

1. A spark impulse source unit for a sound wave generator comprising alinearly-extended electrode having a terminal portion at one end, arelatively thin layer of liquid of low conductivity laying alongsidesaid linearlyextended electrode along the length thereof, said layerhaving on its side facing away from said electrode a spark guidingsurface generally paralleling said linearlyextended electrode andintersecting said terminal portion thereof, a discharge electrode forinitiating a spark discharge to said spark guiding surface of saidliquid layer positioned at a point located opposite saidlinearly-extended electrode and a substantial distance from saidterminal portion, and means for impressing across said electrodes a hightension voltage pulse so as to create a sudden spark discharge of shortduration between said discharge electrode and said terminal portion ofsaid linearly-extended electrode at the point of intersection of saidspark guiding surface therewith in a path along said spark guidingsurface of said liquid layer.

2. A spark impulse source unit for a sound wave generator comprising alinearly-extended electrode having a terminal portion at one end, arelatively thin layer of liquid of low conductivity laying alongsidesaid linearlyextended electrode along the length thereof, said layerhaving on its side facing away from said electrode a spark guidingsurface generally paralleling said linearlyextended electrode andintersecting said terminal portion thereof, a discharge electrode forinitiating a spark discharge to said spark guiding surface of saidliquid layer positioned at a point located opposite saidlinearly-extended electrode and a substantial distance from saidterminal portion, and means for periodically impressing a high tensionvoltage pulse across said electrodes so as to create a succession ofspark discharges of short duration between said discharge electrode andsaid terminal portion of said linearly-extended electrode at the pointof intersection of said spark guiding surface therewith in a path alongsaid spark guiding surface of said liquid layer.

3. A spark impulse source for a sound wave generator comprising meansproviding an air-liquid interface with a liquid body of relatively lowconductivity, a liquidimmersed linearly-extended electrode closelyspaced from and generally paralleling said interface, saidlinearlyextended electrode having a terminal portion at one end and atip portion at the other, one of which intersects said air-liquidinterface, a discharge electrode positioned in proximity to saidair-liquid interface at a point spaced along said linearly-extendedelectrode from the portion of the latter which intersects saidair-liquid interface, and means for impressing across said electrodes ahigh tension voltage pulse so as to create a sudden spark discharge ofshort duration in a path extending along said air-liquid interfacebetween said discharge electrode and said intersecting portion of saidlinearly-extended electrode.

4. A spark impulse source for a sound wave generator comprising a pancontaining a body of liquid of low conductivity, a linearly-extendedelectrode positioned a relatively short distance below and generallyparallel to the upper surface of said body of liquid, said electrodehaving a submerged tip at one end and a terminal portion at the otherextending upwards through the liquid surface, a discharge electrodepositioned above the liquid surface over said linearly-extendedelectrode at a point substantially spaced from said terminal portion,and means for impressing across said electrodes a high tension voltagepulse so as to create a sudden spark discharge of short duration betweensaid discharge electrode and said terminal portion of saidlinearly-extended electrode in a path including the air space betweensaid discharge electrode and a point of the liquid surface immediatelythereunder, and continued by the liquid surface between said point andsaid terminal portion of said linearly-extended electrode at the pointof intersection of said liquid surface therewith.

5. The subject matter of claim 3, including means for depressing saiddischarge electrode toward the surface of said liquid body.

6. A spark impulse source for a sound generator comprising sparkterminals and a spark gap therebetween, a body of liquid of relativelylow conductivity having a surface paralleling and bounding said gap fora substantial distance, a linearly-extended electrode connected to oneof said terminals immersed within said body of liquid and relativelyclose-spaced from and substantially paralleling said liquid surface, andmeans for impressing across said terminals a high tension voltage pulseso as to cause a sudden spark discharge of short duration across saidgap adjacent said bounding liquid surface.

7. A spark impulse source for a sound generator comprising sparkterminals and a spark gap therebetween, a body of liquid of relativelylow conductivity, and air forming an air-liquid interface parallelingand bounding said gap for a substantial distance, a linearly-extendedelectrode connected to one of said terminals relatively closely-spacedfrom and substantially paralleling said interface, and means forimpressing across said terminals a high tension voltage pulse so as tocause a sudden spark discharge of short duration across said gapadjacent said bounding air-liquid interface.

8. A spark impulse source for a sound generator comprising a containerholding a body of liquid of relatively low conductivity, an insulationbody in said body of liquid having an extended surface in contact withsaid liquid, a pair of spark terminals positioned in proximity to theplane of said extended surface and spaced a substantial distance apartso as to form a spark gap, a substantial extended length of which isalong said plane, at least one of said terminals being substantially insaid plane, a linearly-extended electrode connected to one of said sparkterminals and extending generally parallel to said surface in relativelyclose-spaced relation thereto, and means for impressing a high tensionvoltage pulse across said terminals to create a sudden spark dischargeof short duration in a path along said surface in parallelism to saidlinearly-extended electrode.

9. A spark impulse source for a sound generator comprising a containerholding a body of liquid of relatively low conductivity, an insulationbody in said body of liquid having two opposite and generally parallelextended surfaces, at least one of which is in contact with said body ofliquid, a pair of spark terminals positioned substantially in the planeof said last-mentioned surface, so as to form an extended spark gaptherebetween along said surface, a linearly-extended electrode connectedto one of said terminals and extending along the other of said surfacesof said insulation body in general parallelism to said spark gap, andmeans for impressing a high tension voltage pulse between said terminalsto create a sudden spark discharge of short duration along said sparkgap.

References Cited in the file of this patent UNITED STATES PATENTS400,366 Sedgwick Mar. 28, 1889 537,402 Burton and Engell Apr. 9, 1895537,404 Burton Apr. 9, 1895 921,013 Shoemaker May 11, 1909

